Electrode for projection apparatus.



M. H. MOFFETT.

ELECTRODE FOR PROJECTION APPARATUS.

APPLICATION FILED OCT. I. 1913- Patented Dec. 28, 1915.

l/VVE/VTOR MARCH-5 H. MUFFETT 0\% ATTORNEY coLuMmA PLANOGRAPH 60..WASHINGTON. n. c.

IMABCUS H. MOFFETT, OF LAKEEVOOD, 0H1

0, ASSIGNOR TO NATIONAL CARBON COM- PANY, OF CLEVELAND, 03-110, ACORPORATION 01 NEW JERSEY.

ELECTRODE FOB PROJECTION APPARATUS.

Application filed October 1, 1913.

To all whom it may concern:

Be it known that I, Mantras H. Morrn'rr, a citizen of the United St tes,residing at Lakewood, in the county of (luyahoga and State of Ohio, haveinvented a certain new and useful Improvement in Electrodes forProjection Apparatus, of which the following is a full, clear, and exactdescription.

This invention relates to an improvement in electrodes for use inprojection apparatus.

The invention is intended primarily to be applied to carbon electrodesfor small and inexpensive projection lamps such as are used quiteextensively in schools, fraternal societies and in the hon This type ofprojection lamp has no means for feeding the carbons together, theoperation being performed by grasping the outer ends of the carbons inthe hands and simultaneously pushing them inward through the holderuntil the desired length of arc is obtained. Since the drop around thearc is considerable, it is obvious that the operator would receive anannoying shock each time the adjustment is made unless insulating glovesare worn. Gloves are cumbersome and inconvenient and I have made myimprovement with the idea of eliminating their use.

One object of my invention is therefore to secure a cheap and convenientinsulation for the end of the electrodes.

Another object is to provide means on the end of the electrodes to breakthe circuit before they are pushed so far within the holder that theycannot be withdrawn from the outside of the lamp.

In the drawings, Figure 1 is a top view of a projection apparatus withmy invention applied thereto. Fig. 2 is an enlarged cross section of oneof the electrode holders with the electrode in the cutout position. Fig.3 is an enlarged end view of the electrode holder with part removed toshow the contact and gripping arrangement.

In the drawing, 1 is the main casing of the apparatus containing thecondensing arrangement and 2 is the usual adjustable proj ection part ofthe apparatus. The electrodes 8 and a usually consisting of coredcarbons passed through insulating bushings 5 and 6 which have means,such as a spring 7 and a V shaped metallic part 8, for making theelectrical connection and holding the electrodes in their adjustedpositions. Binding posts 9 pass through the bushings 5 and 6 and areSpecification of Letters Patent.

Patented Dec. 28,1915.

Serial No. 792,704.

secured to the V shaped members 8. The terminal wires are fastened tothe binding posts 9 in the usual way (not shown).

My invention relates to an adherent insulating coating 10 applied to theends of the elect-rode. The insulating coating which has been found mostsatisfactory, due to the simplicity of its application, is water glass,or sodium silicate. This may be applied by dipping one end of eachelectrode a short distance in a water glass solution. Upon drying, agood and very adherent insulating coating is formed which the operatormay grasp for adjusting the electrodes without receiving a. shock. Itwill be evident that other hardening insulating substances such as pitchor asphalt may be used, but I have found water glass to be preferable.

With the usual type of electrode, it frequently happens that theoperator will accidentally push it so far in the bushing or holder thatit cannot be withdrawn or further adjusted with out extinguishing thearc and opening up the apparatus to push it back with a pencil or otherinstrument. This frequently happens when the carbons are almost consumedand the operator thinks that they can be adjusted a slight ad ditionalextent before being removed. lVhenever the electrodes are thus adjustedso far in the bushing that they cannot be withdrawn from the outside, itis annoying to the operator as well as to the spectators to 11 re thelamp shut down for a minute or two until the electrodes can be pushedout so that new ones can be inserted. My invention is designed toprevent this annoyance. The insulating coating is of sutlicient lengthto pass under the contact spring and break the contact while theelectrode end still projects from the bushing a suliicient distance tobe readily grasped by the operator. It will thus be seen that thecircuit will be interrupted and the arc extinguished before theelectrode has been consumed to a point where it may accidentally bepushed into the bushing beyond the grasp of the operator. As soon as thearc is extinguished, the re maining electrode, or electrodes, can beremoved and new ones inserted so that the operation of the lamp is onlyinterrupted for a second or two.

The thickness of the insulating coating on the electrodes may vary butit should preferably be of no appreciable thickness so that theelectrodes can be properly packed and shipped- The length of the bushingof course may be varied, but with the usual type of lamp, it Will befound that an inch or an inch and a half Will be the proper length tofurnish a convenient insulation for the safety of the operator as Wellas the automatic cut-out previously described.

Having described my invention, what 1 claim is:

1. An electrode for projection apparatus having an adhering coating ofan insulating substance on one end.

2. An electrode for projection apparatus having a coating of Water glasson one end,

the remaining surface of the electrode being conducting.

3. In projection apparatus the combination of the holder With a contactdevice and anelectrode having a coating of an insulating substance onone end adapted to pass under said contact device to interrupt thecircuit before the electrodes are completely adjusted Within saidholder.

In testimony whereof, I hereunto affix my signature.

IVIARCUS H. IVIOFFETT Witnesses W W. DOW DELL, H. G. GRovER.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. C.

